kernel+libc: Add dup2()

kernel/src/sys/file.cpp

@@ -147,3 +147,22 @@ Result<u64> sys_ioctl(Registers*, SyscallArgs args)
 
     return descriptor.inode->ioctl(request, arg);
 }
+
+Result<u64> sys_dup2(Registers*, SyscallArgs args)
+{
+    int oldfd = (int)args[0];
+    int newfd = (int)args[1];
+
+    Thread* current = Scheduler::current();
+
+    if (newfd < 0 || newfd >= FD_MAX) return err(EBADF);
+
+    auto descriptor = *TRY(current->resolve_fd(oldfd));
+
+    if (newfd == oldfd) return (u64)newfd;
+
+    current->fd_table[newfd] = descriptor;
+    current->fd_table[newfd]->flags &= ~O_CLOEXEC;
+
+    return (u64)newfd;
+}

libc/include/unistd.h

@@ -103,6 +103,9 @@ extern "C"
     /* Duplicate a file descriptor. */
     int dup(int fd);
 
+    /* Replace a file descriptor with a copy of another one. */
+    int dup2(int oldfd, int newfd);
+
     /* Change the current working directory. */
     int chdir(const char* path);
 

libc/src/unistd.cpp

@@ -292,6 +292,12 @@ extern "C"
         return fcntl(fd, F_DUPFD, 0);
     }
 
+    int dup2(int oldfd, int newfd)
+    {
+        long rc = syscall(SYS_dup2, oldfd, newfd);
+        __errno_return(rc, int);
+    }
+
     int chdir(const char* path)
     {
         long rc = syscall(SYS_chdir, path);

libluna/include/luna/Syscall.h

@@ -4,7 +4,7 @@
     _e(exit) _e(clock_gettime) _e(mmap) _e(munmap) _e(usleep) _e(openat) _e(close) _e(read) _e(getpid) _e(write)       \
         _e(lseek) _e(mkdir) _e(execve) _e(mknod) _e(fork) _e(waitpid) _e(getppid) _e(fcntl) _e(getdents) _e(getuid)    \
             _e(geteuid) _e(getgid) _e(getegid) _e(setuid) _e(setgid) _e(seteuid) _e(setegid) _e(chmod) _e(chown)       \
-                _e(ioctl) _e(fstatat) _e(chdir) _e(getcwd) _e(unlinkat) _e(uname) _e(sethostname)
+                _e(ioctl) _e(fstatat) _e(chdir) _e(getcwd) _e(unlinkat) _e(uname) _e(sethostname) _e(dup2)
 
 enum Syscalls
 {